The HNOSS horizontal cryostat and its valve box upon reception at the FREIA Laboratory (Image: Uppsala University)

HNOSS (Horizontal Nugget for Operation of Superconducting Systems) is a versatile horizontal cryostat system for testing superconducting cavities located at the FREIA Laboratory, Department of Physics and Astronomy, Uppsala University, Sweden.

The facility allows users to characterize 1-2 superconducting cavities at a time at either low or high RF power. Each cavity must be equipped with a helium tank and optionally with a fundamental power coupler and a tuning system.  The range of operation is 1.8 to 4.5~K.

A project based at HNOSS is expected to last typically for three months. It is estimated that the installation of equipment will take one month, followed by a month of cooling and measurement, and finally a month to warm up the facility so equipment can be removed.


  • 3 x high power RF amplifier stations at 352 and 400 MHz (for both CW and pulsed operations)
  • Self-excited loop for low power operation (up to 1 kW RF power)
  • Standard measurement equipment, ie vector network analyser, frequency generator, oscilloscope.
  • Data acquisition and monitoring system
  • Mechanical and electric workshop services (for installation and maintenance)

Support offered

Users can choose to participate in the installation work or leave this preparation to facility staff. Preparation and installation of the experiment is expected to take one month followed by a week of cool down, to allow the facility to reach the required state for operation. Measurements are expected to last for two weeks and finally a week to warm the facility up to allow equipment to be uninstalled.

Facility staff will operate the facility and will be available to advise and assist with testing scenarios. Users can take the lead during the measurement campaign.

Logistics support can be arranged through local providers by facility staff.


Interested parties are encouraged to contact the Facility Coordinator before beginning the formal application process with brief details of the test campaign proposal. 

HNOSS Facility Coordinator: Roger Ruber